U.S. patent application number 15/035507 was filed with the patent office on 2016-10-06 for method for surface scanning in medical imaging and related apparatus.
This patent application is currently assigned to DANMARKS TEKNISKE UNIVERSITET. The applicant listed for this patent is DANMARKS TEKNISKE UNIVERSITET. Invention is credited to Rasmus Ramsbol JENSEN, Rasmus LARSEN, Oline OLESEN, Jakob WILM.
Application Number | 20160287080 15/035507 |
Document ID | / |
Family ID | 49584619 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160287080 |
Kind Code |
A1 |
OLESEN; Oline ; et
al. |
October 6, 2016 |
METHOD FOR SURFACE SCANNING IN MEDICAL IMAGING AND RELATED
APPARATUS
Abstract
A method and apparatus for surface scanning in medical imaging
is provided. The surface scanning apparatus comprises an image
source, a first optical fiber bundle comprising first optical
fibers having proximal ends and distal ends, and a first optical
coupler for coupling an image from the image source into the
proximal ends of the first optical fibers, wherein the first
optical coupler comprises a plurality of lens elements including a
first lens element and a second lens element, each of the plurality
of lens elements comprising a primary surface facing a distal end
of the first optical coupler, and a secondary surface facing a
proximal end of the first optical coupler.
Inventors: |
OLESEN; Oline; (Soborg,
DK) ; LARSEN; Rasmus; (Gentofte, DK) ; WILM;
Jakob; (Copenhagen N, DK) ; JENSEN; Rasmus
Ramsbol; (Frederiksberg C, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DANMARKS TEKNISKE UNIVERSITET |
Kgs. Lyngby |
|
DK |
|
|
Assignee: |
DANMARKS TEKNISKE
UNIVERSITET
Kgs. Lyngby
DK
|
Family ID: |
49584619 |
Appl. No.: |
15/035507 |
Filed: |
November 13, 2014 |
PCT Filed: |
November 13, 2014 |
PCT NO: |
PCT/EP2014/074509 |
371 Date: |
May 10, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 6/527 20130101;
G02B 6/32 20130101; A61B 2562/228 20130101; G02B 6/06 20130101;
A61B 5/721 20130101; A61B 5/0046 20130101; A61B 6/032 20130101;
A61B 5/0064 20130101; A61B 6/037 20130101; A61B 5/1128 20130101;
A61B 5/055 20130101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61B 6/00 20060101 A61B006/00; A61B 6/03 20060101
A61B006/03; A61B 5/055 20060101 A61B005/055; A61B 5/11 20060101
A61B005/11 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 2013 |
EP |
13192786.5 |
Claims
1-22. (canceled)
23. A method for surface scanning in medical imaging, the method
comprising providing an image source and a first fiber bundle
comprising first optical fibers having proximal ends and distal
ends, wherein the image source has a resolution of 480.times.320
pixels or more, the number of first optical fibers is larger than
1,000 and the first fiber bundle has a length larger than 1 meter;
positioning the distal ends of the first optical fibers within a
scanner borehole of a medical scanner; feeding an image from the
image source into a proximal end of a first optical coupler, the
first optical coupler comprising a plurality of lens elements
including a first lens element and a second lens element; feeding
an image from a distal end of the first optical coupler into the
proximal ends of the first optical fibers.
24. Method according to claim 23, wherein the image source includes
a digital micromirror device (DMD) chip.
25. Method according to claim 23, wherein the image source is
connected to a control unit for receiving control signal(s) from
the control unit, the control signal(s) comprising a pattern
sequence selector, and wherein the image source is configured for
projecting different pattern sequences dependent on the pattern
sequence selector.
26. Method according to claim 25, wherein a number of different
pattern sequences are stored in the image source, and the image
source is configured to project a selected pattern sequence based
on the pattern sequence selector from the control unit.
27. Method according to claim 23, wherein the image source
comprises a light source, and a mirror or a prism is used to guide
light from the light source towards the first optical coupler.
28. Method according to claim 23, wherein the first optical coupler
is a relay lens coupler.
29. Method according to claim 23, wherein the distal end of the
first optical coupler is releasably secured to the proximal end of
the first fiber bundle by a click-release-coupling.
30. Method according to claim 23, wherein the distal end of the
first optical coupler is fixed non-releasably to the proximal end
of the first fiber bundle.
31. Method according to claim 23, the method comprising providing a
second optical coupler comprising a plurality of lens elements
including a first lens element and a second lens element; providing
a second fiber bundle comprising second optical fibers having
proximal ends and distal ends; positioning the distal ends of the
second optical fibers within the scanner borehole of the medical
scanner; capturing a projected image from a subject in the borehole
by the distal ends of the second optical fibers; and feeding the
projected image from the proximal end of the second optical fibers
into the second optical coupler.
32. Method according to claim 23, wherein feeding an image from the
image source comprises feeding a pattern sequence comprising a
plurality of different patterns.
33. Surface scanning apparatus for surface scanning in medical
imaging, the apparatus comprising an image source having a
resolution of 480.times.320 pixels or more, a first optical fiber
bundle comprising first optical fibers having proximal ends and
distal ends, wherein the number of first optical fibers is larger
than 1,000 and the first fiber bundle has a length larger than 1
meter, and a first optical coupler for coupling an image from the
image source into the proximal ends of the first optical fibers,
wherein the first optical coupler comprises a plurality of lens
elements including a first lens element and a second lens element,
each of the plurality of lens elements comprising a primary surface
facing a distal end of the first optical coupler, and a secondary
surface facing a proximal end of the first optical coupler.
34. Surface scanning apparatus according to claim 33, wherein the
image source includes a digital micromirror device (DMD) chip.
35. Surface scanning apparatus according to claim 33, wherein the
image source is connected to a control unit for receiving control
signal(s) from the control unit, the control signal(s) comprising a
pattern sequence selector, and wherein the image source is
configured for projecting different pattern sequences dependent on
the pattern sequence selector.
36. Surface scanning apparatus according to claim 35, wherein a
number of different pattern sequences are stored in the image
source, and the image source is configured to project a selected
pattern sequence based on the pattern sequence selector from the
control unit.
37. Surface scanning apparatus according to claim 33, wherein the
first optical coupler comprises an even number of lens
elements.
38. Surface scanning apparatus according to claim 33, wherein the
first optical coupler is a relay lens coupler.
39. Surface scanning apparatus according to claim 33, wherein the
distal end of the first optical coupler is releasably secured to
the proximal end of the first fiber bundle by a
click-release-coupling.
40. Surface scanning apparatus according to claim 33, wherein at
least one of the plurality of lens elements is achromatic.
41. Surface scanning apparatus according to claim 33 wherein the
first lens element is positioned at the proximal end of the first
optical coupler and the second lens element is positioned at the
distal end of the first optical coupler, wherein the first lens
element and the second element are achromatic with convex sides
pointing towards each other.
42. Surface scanning apparatus according claim 33, wherein the
primary surface of each of the plurality of lens elements is
concave or convex, and the secondary surface of each of the
plurality of lens elements is concave or convex.
Description
[0001] The present invention relates to a method and apparatus for
surface scanning in medical imaging, in particular in magnetic
resonance imaging (MRI), in positron emission tomography (PET),
and/or in combined MRI/PET. The invention may be used for surface
scanning/motion tracking in particular inside small geometries
(in-bore of PET, MRI, CT, SPECT or combined scanners as PET/CT and
MRI/PET).
BACKGROUND
[0002] Over the last decade, numerous methods for surface scanning
and motion tracking in brain imaging have been developed, but head
motion during scanning pertains to be a significant problem causing
artefacts and significantly reducing image quality.
[0003] Known methods include external tracking systems as well as
image based motion tracking and correction. Many external tracking
systems use markers attached to the subjects head. This potentially
introduces errors and complicates the process of preparing the
subject for the scan and therefore reduces the usability in
clinical practice. Correspondingly, the image based motion tracking
methods developed for medical brain imaging generally suffer from
an inability to obtain sufficiently high temporal and spatial
resolution at the same time. Further, the high resolution of modern
medical scanners (down to tenths of a millimeter for MRI and a few
millimeters for PET) set strict requirements to motion tracking
systems.
SUMMARY
[0004] The present invention relates to a method and apparatus for
improved surface scanning in medical imaging. Disclosed herein is
therefore a method for surface scanning in medical imaging that may
be used for subject tracking, the method comprising a) providing an
image source and a first fiber bundle comprising first optical
fibers having proximal ends and distal ends; b) positioning the
distal ends of the first optical fibers within a scanner borehole
of a medical scanner; c) feeding an image from the image source
into a proximal end of a first optical coupler, the first optical
coupler comprising a plurality of lens elements including a first
lens element and a second lens element; and d) feeding an image
from a distal end of the first optical coupler into the proximal
ends of the first optical fibers.
[0005] Disclosed herein is also a surface scanning apparatus for
surface scanning in medical imaging, the apparatus comprising a) an
image source, b) a first optical fiber bundle comprising first
optical fibers having proximal ends and distal ends, and c) a first
optical coupler for coupling an image from the image source into
the proximal ends of the first optical fibers, wherein the first
optical coupler comprises a plurality of lens elements including a
first lens element and a second lens element, each of the plurality
of lens elements comprising a primary surface facing a distal end
of the first optical coupler, and a secondary surface facing a
proximal end of the first optical coupler.
[0006] By the above method and/or surface scanning apparatus is
obtained an improved surface scanning method and/or motion tracking
method wherein components that generate noise, such as radio
emitting components and/or ferromagnetic components, are separated
form and kept out of the bore. Further, occlusion effects are
highly reduced if not completely avoided. Further, an improved
image quality on the object which is scanned in the borehole is
provided. Problems previously observed regarding a decrease in
image quality due to long distances between scanner and light
source is avoided due to the use of optical fibers, which ensures a
high image quality even over larger distances.
[0007] The method may be particularly useful in a method for motion
tracking in medical imaging, and the surface scanning apparatus may
be a motion tracking apparatus
[0008] By the method and/or surface scanning apparatus is further
obtained a very compact device, which can easily be incorporated
into a scanner or be used as an add-on to existing scanning
systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The above and other features and advantages of the present
invention will become readily apparent to those skilled in the art
by the following detailed description of exemplary embodiments
thereof with reference to the attached drawings, in which:
[0010] FIG. 1a schematically illustrates a surface scanning
apparatus in connection with a medical scanner and a computer
system,
[0011] FIG. 1b schematically illustrates an exemplary surface
scanning apparatus,
[0012] FIG. 2 schematically illustrates parts of an exemplary
surface scanning apparatus,
[0013] FIG. 3 schematically illustrates parts of an exemplary
surface scanning apparatus,
[0014] FIG. 4 schematically illustrates parts of an exemplary
surface scanning apparatus,
[0015] FIG. 5 schematically illustrates parts of an exemplary
surface scanning apparatus,
[0016] FIG. 6a schematically illustrates decreasing of the image
size with different lens elements in an optical coupler,
[0017] FIG. 6b schematically illustrates increasing of the image
size with different lens elements in an optical coupler,
[0018] FIG. 7a schematically illustrates a relay lens coupler,
and
[0019] FIG. 7b schematically illustrates an alternative relay lens
coupler.
DETAILED DESCRIPTION
[0020] The figures are schematic and simplified for clarity, and
they merely show details which are essential to the understanding
of the invention, while other details may have been left out.
Throughout, the same reference numerals are used for identical or
corresponding parts.
[0021] Surface scanning incorporates tracking spatial position of a
surface or surface points over time and/or tracking/determining
spatial position of a surface or surface points at a given
time.
[0022] The medical scanner may be a magnetic resonance (MR)
scanner. Further, the method and apparatus for motion tracking may
be employed for motion correction of scanning images obtained by
other medical scanners, such as a positron emission tomography
[0023] (PET) scanner, a single photon emission computed tomography
(SPECT) scanner or a computed tomography (CT) scanner. In one or
more aspects, the method and apparatus may be employed for motion
correction of a subject in a combined PET-MR scanner or a combined
PET-CT scanner.
[0024] The image source provided in the method or the apparatus may
include a light source and/or a digital micromirror device (DMD)
chip, where the DMD chip is for modulating the incoming light from
the light source thus creating a pre-determined image source.
[0025] The image source may be a modified DLP (digital light
processing) projector.
[0026] Feeding an image, e.g. from the image source into a proximal
end of a first optical coupler and/or from a distal end of the
first optical coupler into the proximal ends of the first optical
fibers, may comprise feeding a pattern sequence comprising a
pattern or a plurality of different patterns.
[0027] The image source may be configured for providing a pattern
sequence, e.g. comprising a plurality of different patterns, e.g.
for projection of patterns onto the surface region or scene of the
subject in the borehole. A pattern sequence (S), e.g. a first
pattern sequence (S1) and/or a second pattern sequence (S2),
comprises one or more patterns (P), such as a plurality of
different patterns including a primary pattern and a secondary
pattern. A pattern sequence comprises or consists of a number N of
patterns. A pattern sequence may be defined by pattern sequence
parameters, for example including number of patterns,
configuration/structure of respective patterns, order of patterns
and/or timing of pattern(s) of the pattern sequence. The duration
of a pattern sequence may be in the range from 1 millisecond to
about 1 second. The duration of a pattern sequence may be about 10
milliseconds, about 20 milliseconds, about 50 milliseconds, about
100 milliseconds or about 200 milliseconds.
[0028] A pattern may comprise a number of pixels, e.g. arranged in
an array along a first and second axis. A pattern may be defined by
pattern parameters, e.g. including pixel settings (color/wavelength
and/or intensity) of each pixel and/or one or more groups of pixels
in the pattern. A group of pixels of a pattern may be referred to
as a subregion denoted R of a pattern. Accordingly, a pattern may
comprise one or more subregions R.sub.1, R.sub.2, R.sub.3, . . . ,
a subregion comprising one or more pixels. Pattern sequence
parameters may include pattern parameters, e.g. of a primary
pattern, a secondary pattern and/or a tertiary pattern.
[0029] The image source may comprise a light modulator.
[0030] The light modulator or DMD chip can be adapted for
projection of patterns onto the surface region or scene of the
subject in the borehole. The light modulator may comprise a liquid
crystal display (LCD) chip or a DMD chip. In one or more
embodiments, the light modulator may comprise a liquid crystal on
silicon (LCOS) chip. In one or more embodiments, the light
modulator may comprise grids, slits or filters. The light modulator
may be a transmitting or reflective light modulator.
[0031] The DMD chip/light modulator may be an array which is
approximately 9.86 mm times 6.16 mm and images from the DMD
chip/light modulator are mapped with the first optical coupler into
a first fiber bundle with proximal end size of about 6.7mm times 5
mm.
[0032] The image source may be connected to a control unit for
receiving control signal(s) from the control unit. The control
signal(s) may comprise pattern sequence parameters, such as number,
configuration, order and/or timing of pattern(s) of the pattern
sequence. In one or more embodiments, the control signal(s) may
comprise a pattern sequence selector, and the image source may be
configured for projecting different pattern sequences dependent on
the pattern sequence selector.
[0033] The resolution of the image source and/or first fiber bundle
limits the pattern resolution projected onto the subject. The image
source may have a resolution of at least 500 pixels, such as at
least 1,000 pixels or at least 10,000 pixels in order to project a
useful image on the subject. In an exemplary method and/or
apparatus, the image source may have a resolution of HVGA
(480.times.320 pixels) or more, e.g. (608.times.684 pixels), SVGA
(800.times.600 pixels), XGA (1024.times.768 pixels), 720p
(1280.times.720 pixels), or 1080p (1920.times.1080 pixels).
[0034] In one or more embodiments, a number of different pattern
sequences may be stored in the image source, and the image source
may be configured to project a selected pattern sequence based on a
pattern sequence selector from a control unit.
[0035] In an embodiment, the light source may include one or more
lasers or (high power) LED's including a first laser/LED configured
to emit light at the first wavelength .lamda..sub.1 and/or a second
laser/LED configured to emit light at a second wavelength
.lamda..sub.2. The light source may also include a third laser/LED
configured to emit light at a third wavelength .lamda..sub.3.
[0036] The light source may include a broad spectrum light source,
such as a metal-halide lamp. In one or more embodiments, the light
source may comprise a light emitting diode (LED). The light source
may comprise a filter for forming light with desired frequency
spectrum/wavelength distribution. In one or more embodiments, the
light source may be adapted to emit light in the infrared (IR) or
near-infrared (NIR) range, for example at a wavelength in the range
from 700 nm to about 1,000 nm, e.g. about 850 nm. In one or more
embodiments, the light source may be adapted to emit light in the
UV range.
[0037] In one or more embodiments, the image source may comprise
light at a first wavelength .lamda..sub.1 in the range from 780-900
nm. For example, the wavelength range may be between 800-860 nm.
The first laser/LED may be a red or orange/red laser, wherein the
first wavelength .lamda..sub.1 is in the range from about 590 nm to
about 700 nm. In one or more embodiments the first wavelength
.lamda..sub.1is about 635 nm. The first laser/LED may be an LED,
wherein the first wavelength .lamda..sub.1 is in the range from
about 830 nm to about 870 nm, e.g. about 850 nm or from about 810
nm to about 850 nm. The first laser/LED may be an LED, wherein the
first wavelength .lamda..sub.1 is in the range from about 790 nm to
about 830 nm, e.g. about 810 nm or from about 800 nm to about 820
nm.
[0038] The second laser/LED may be a green laser, wherein the
second wavelength .lamda..sub.2 is in the range from about 490 nm
to about 560 nm, e.g. about 532 nm. The second laser/LED may be an
LED, wherein the second wavelength .lamda..sub.2 is in the range
from about 880 nm to about 920, e.g. about 900 nm.
[0039] The third laser/LED may be a blue or violet laser, e.g.
wherein the third wavelength .lamda..sub.3 is in the range from 430
nm to about 490 nm, e.g. about 445 nm or about 473 nm. The third
laser/LED may be an LED, e.g. wherein the third wavelength
.lamda..sub.3 is in the range from 930 nm to about 1,000 nm, e.g.
about 940 nm.
[0040] The light source may comprise a UV source, e.g. configured
to emit light with a wavelength in the range from about 230 nm to
about 400 nm, e.g. about 350 nm.
[0041] One or more mirrors or a prism may be used to guide light or
an image from the light source and/or image source to the first
optical coupler. Different examples of this are shown and described
in connection with FIG. 2-5.
[0042] The first optical coupler may comprise or consist of an even
number of lens elements, e.g. two, four, six, eight, ten, twelve or
more lens elements. In one or more embodiments, ten lenses are
included in the first optical coupler. In another embodiment, six
lenses are included in the first optical coupler. When choosing a
lower number of lenses, the optical loss is kept at a minimum,
whereas when choosing a many lenses, the image quality is improved
and the distortion and blurriness are reduced. The relay lens
element may comprise between four and twelve lens elements.
[0043] The first optical coupler may be adapted for either
increasing or decreasing the size of the image after the image has
passed through the first optical coupler. In an exemplary
method/apparatus, the lens elements in the first optical coupler
maps the incoming image size by a ratio of 1:1.2, thus the image
size of the image coming out of the distal end of the first optical
coupler is 20% larger compared to the size of the image entering
the first optical coupler at its proximal end. In general, the
image size can be mapped in the range from 1:0.5 (i.e. the
out-coming image is 50% smaller than the incoming image) to
1:2.
[0044] Advantageously, the first optical coupler may be a relay
lens coupler.
[0045] The distal end of the first optical coupler may be secured
releasably to the proximal end of the first fiber bundle by a
click-release-coupling. This allows for an easy and flexible
positioning of the optical fibers in the borehole of the scanner or
an easy replacement and/or exchange of the optical fibers or the
first optical coupler without moving the other of the two.
[0046] Alternatively, for ensuring a constant optimum coupling of
the image from the first optical coupler into the optical fibers,
the distal end of the first optical coupler may be fixed
non-releasably to the proximal end of the first fiber bundle.
[0047] A second optical coupler comprising a plurality of lens
elements including a first lens element and a second lens element
may also be included in the surface scanning apparatus and/or the
method for tracking the motion. Also, a second fiber bundle
comprising second optical fibers having proximal ends and distal
ends can be provided and its distal ends positioned within the
scanner borehole of the medical scanner. The distal ends of the
second optical fibers may be applied for capturing a projected
image from a subject in the borehole. This projected image will
normally be fed from the proximal ends of the second optical fibers
into the second optical coupler.
[0048] The second optical coupler may also be adapted for either
increasing or decreasing the size of the projected image after the
image has passed through the second optical coupler.
[0049] At least one of the plurality of lens elements in the first
and/or second optical coupler may be achromatic.
[0050] In an embodiment of the invention, the first lens element in
the first and/or second optical coupler can be positioned at the
proximal end of the first and/or second optical coupler,
respectively, and the second lens element can be positioned at the
distal end of the first and/or second optical coupler,
respectively. The first lens element and the second element may
further be achromatic with convex sides pointing towards each
other.
[0051] The primary surface of each of the plurality of lens
elements in the first and/or second optical coupler may be concave
or convex or planar or a combination thereof. Likewise, the
secondary surface of each of the plurality of lens elements in the
first and/or second optical coupler may be concave or convex or
planar or a combination thereof. The primary surface of one or more
lens elements may be concave. The primary surface of one or more
lens elements may be convex. The primary surface of one or more
lens elements may be plane. The secondary surface of one or more
lens elements may be concave. The secondary surface of one or more
lens elements may be convex. The secondary surface of one or more
lens elements may be plane.
[0052] The apparatus and the method may further comprise a mirror
and/or a prism, and light from the light source may pass the
mirror/prism before entering the first optical coupler.
[0053] The first optical fibers may further be adapted for
projecting at least one pattern from the image source via the first
optical fibers onto the surface region of the subject positioned in
a borehole of the medical scanner.
[0054] The first optical fibers may comprise at least 100 optical
fibers, such as at least 10,000 fibers, each fiber corresponding to
a pixel in a pattern projected onto the surface region of the
subject. In one or more embodiments, the number of first optical
fibers is equal to or larger than the number of pixels in the image
source, for full benefit of the image source resolution. The number
of first optical fibers may match or be in the range of .+-.20% of
the resolution of the image source. In one or more embodiments, the
number of first optical fibers is less than the number of pixels in
the image source, for full benefit of the optical fibers.
[0055] The second optical fibers can be adapted for capturing at
least one projected pattern and/or image projected form the
subject. The second optical fibers may comprise at least 100
optical fibers, such as at least 100,000 fibers. Each second
optical fiber may correspond to one or more pixels in a first
camera, which the captured image is transmitted to. In one or more
embodiments, the number of second optical fibers is equal to or
larger than the number of pixels in the first camera for increasing
the processing time of the camera. In one or more embodiments, the
number of second optical fibers is less than the number of pixels
in the first camera for increasing the precision of the image
capturing. The number of second optical fibers may match or be in
the range of .+-.50% of the resolution of the first camera.
[0056] The first camera may be a CCD camera or a CMOS camera. The
first camera may have a resolution of at least 640.times.480, e.g.
1280.times.960, 3264.times.2448 or more.
[0057] The surface region may have an area of at least 0.1
cm.sup.2, e.g. in the range from 1 cm.sup.2 to 500 cm.sup.2. In one
or more embodiments, the surface region area may be in the range
from 20 cm.sup.2 to 100 cm.sup.2.
[0058] The surface region may at least partly cover a nasal region
of the subject. This may lead to improved motion tracking due to
the significant curvature of the subject surface in this region.
Further, facial movements are limited near the bridge of the nose
which is preferred when tracking the motion of the scull and the
brain.
[0059] The apparatus may also comprise a first lens assembly, i.e.
projector side projection optics, arranged at and/or attached to
the distal end of the first optical fibers for coupling images or
pattern sequences from the first optical fibers to the surface
region of the subject. The distal ends of the second optical fibers
may be provided with a second lens assembly, i.e. image capturing
optics, for coupling images or pattern sequences from the surface
region of the subject to the second optical fibers.
[0060] The apparatus may comprise a frame, wherein the first and
second lens assemblies are mounted on the frame. The frame fixes
the position between the two distal ends of the fibers bundles
and/or between the first and second lens assemblies to maintain a
fixed positional relationship in order to provide an accurate
movement correction and/or such that the two fiber bundles can be
moved together inside the borehole. The distal ends of the first
and the second fiber bundles may be mounted on the frame.
[0061] The first and second lens assemblies will normally comprise
an objective lens with a given focal length and an aperture. The
focal length may be changed by exchanging the objective lens. Also
by changing the distance between the objective lens and the distal
ends of the optical fibers in the first or second optical fiber
bundle, control of how much of the image source illuminates the
subject and which area projected light is captured from,
respectively, can be obtained. The aperture in the first and/or
second lens assemblies may be adjusted by opening and/or closing
them, which also provides a tool for controlling the output from
the first optical fibers onto the subject, and the projected image
from the subject into the second optical fibers for the first lens
assembly and the second lens assembly, respectively.
[0062] The second lens assembly may also comprise a filter, e.g. a
NIR filter. Likewise, the first lens assembly may also comprise a
filter.
[0063] The first lens assembly may comprise a first mirror/prism.
The second lens assembly may comprise a second mirror/prism,
respectively. A common mirror/prism may be shared between the first
lens assembly and the second lens assembly. A mirror/prism in a
lens assembly may provide redirection of the light which may lead
to larger freedom in positioning the distal fiber ends/lens
assemblies in the bore.
[0064] The first and second optical fibers may be arranged in
respective first and second fiber arrays. In one or more
embodiments, the first optical fibers may comprise a first array of
at least 10,000 fibers, such as 100.times.100 fibers, such as
400.times.400 or 600.times.600 fibers or 680.times.480 fibers or
1,200.times.1,200 fibers or more. The first optical fibers may
comprise a first array of at least 100,000 fibers, e.g.
5,000.times.5,000 fibers. In one or more embodiments, the second
optical fibers comprise a second array of at least 10,000 fibers,
such as 100.times.100 fibers, such as at least 400.times.400 or
600.times.600 fibers or 680.times.480 fibers or 1,200 .times.1,200
fibers, or more. The second optical fibers may comprise a second
array of at least 100,000 fibers, e.g. 5,000.times.5,000 fibers.
The optical fibers may be arranged in an array of any suitable size
and shape, e.g. rectangular, circular, oval, polygonal or others.
Typically, the fiber diameter is in the range from 5 to 20
micrometers. The number of first optical fibers may be larger than
1,000, such as larger than 10,000. The number of second optical
fibers may be larger than 1,000, such as larger than 10,000.
[0065] Using first and second optical fibers enables or facilitates
the use of the method and apparatus for medical scanners with a
permanent magnetic field surrounding the object, e.g. an MR
scanner. Further, using first and second optical fibers enables or
facilitates the use of the method and apparatus for medical
scanners with limited access to the subject due to the subject
being positioned in a scanner borehole during scanning.
[0066] The first and second fiber bundles may each have a length
larger than 1 meter, such as larger than 2 meters, e.g. about 5
meters or about 10 meters. In an exemplary apparatus and/or method,
the first and second fiber bundles may each have a length between 1
and 5 meters, such as between 2.5 and 3 meters, for example about
2.7 meters. Having a length of the fiber bundles in this length
range may enable the user to place the distal ends of the first and
second fiber bundles inside the scanner while keeping the first
and/or second optical couplers at a different location remote from
the scanner or even remote from/outside the scanning room.
[0067] The length of the fiber bundles allows for positioning of a
power management part and/or a computer for controlling a sequence,
an image pattern or similar relating to the image source, outside
the room with the scanner. This allows for the creation of a remote
surface scanner. By separating the electronics from the optical end
by the two fibers bundles, a compact, radio frequency noiseless and
low attenuation surface scanner is achieved.
[0068] In the apparatus and method of this invention, a minimum of
components are located in the borehole of the scanner and the
disturbing components are kept outside the borehole. This maintains
the field of view and the high resolution of nowadays surface
scanners. Further, the components located in the borehole of the
scanner may be made of non-metallic materials.
[0069] The surface scanning apparatus may also comprise a housing
which surrounds all the motion tracking elements apart from the
fibers bundles which extend from the surface of the housing. The
housing may be a radio frequency shielded box costume normally made
out of a frame covered by a thin copper layer or sheet, e.g. of a
thickness of 1 mm. Any metal suited for shielding the electric
components may be used.
[0070] A filter of one or more capacitors may ensure that the
electromagnetic noise from powering the components inside the
housing does not propagate along the power cable. Correspondingly,
a power supply is positioned outside the scanner room and the power
is led though a filter in the wall into the scanner room and the
inside of the housing to feed the relevant components therein.
[0071] The surface scanning apparatus may be constructed such that
it is part of the medical scanner or be used as an add-on to
existing scanners.
[0072] Fig. la schematically illustrates a medical scanner 30 for
use with the method and apparatus. The scanner 30 is an MR scanner
comprising a permanent magnet 32 in a scanner housing 34 forming a
scanner borehole 36. The scanner 30 comprises a head coil 38 for
scanning a subject positioned on the support structure (scanner
bed) 39.
[0073] First lens assembly 42 and second lens assembly 44 are
mounted to respective distal ends of first optical fibers 16 and
second optical fibers 20 and positioned in the scanner borehole 36
for projecting and detecting pattern sequences on/from a surface
region within the head coil 38.
[0074] As an alternative to the MR scanner shown in FIG. 1a, PET
scanner comprising at least one detector ring in a scanner housing
forming a scanner borehole could also be imagined. In this case,
the distal ends of the respective optical fibers 16, 20 could be
positioned outside the detector ring and near the scanner borehole
for projecting and detecting pattern sequences on/from a surface
region within the scanner borehole. Yet an alternative to the MR
scanner of FIG. 1a is a combined MR/PET scanner.
[0075] FIG. 1a shows a surface scanning apparatus 2 which is
positioned inside the scanner room defined by surrounding walls 52
illustrated by one wall/Faraday cage to the left side of the
apparatus 2. A power management and/or controller part 50, e.g. a
computer as illustrated in FIG. 1a, is positioned outside the
scanner room. The surface scanning apparatus 2 may be positioned
outside the scanner room defined by surrounding walls 52 if the
optical fibers 16, 20 are sufficiently long.
[0076] In FIG. 1a is also shown an optical extender 54 which
transfers image data noiseless between the surface scanning
apparatus 2 and the computer 50 outside the scanner room. The
apparatus 2 can be surrounded by a housing 4 which functions as a
radio frequency shielded box. The housing 4 can be made out of a
frame, e.g. a wooden frame, covered by a 1 mm copper layer. A
filter of capacitors (not shown in the figure) ensures that the
electromagnetic noise from powering the components inside the
housing does not propagate along the power cable. The power supply
optionally being a separate power supply or a part of the power
management/controller part 50 is positioned outside the scanner
room and the power is led through a filter in the wall 52 into the
scanner room and the elements inside the housing 4 of the apparatus
2.
[0077] The distal ends of fibers are provided with respective first
and second lens assemblies 42, 44 constituting projection optics
and image capturing optics, respectively. A frame 46 is used for
fixing the position between the first and second lens assemblies
42, 44 and/or between the distal ends of the first and second
optical fibers 16, 18, respectively.
[0078] The first and second lens assemblies may each comprise an
objective lens with a given focal length and aperture. Also, the
second lens assembly may comprise a near infra-red (NIR) filter.
Both first and second lens assemblies may comprise a first
mirror/prism and/or second mirror/prism, respectively. The
mirror/prism may be shared between the two lens assemblies.
[0079] FIG. 1b schematically shows a surface scanning apparatus 2
of the present invention. The apparatus 2 comprises a housing 4
accommodating a control unit 6 and an image source 8 comprising a
light source 10 and a light modulator 12. Further, the apparatus 2
optionally comprises a first camera 14 connected to the control
unit 6 for exchange of control signals and/or pattern sequence data
between the control unit 6 and the first camera 14. During use,
first optical fibers 16 are coupled to the apparatus at the
proximal ends 17 of the first optical fibers via first optical
coupler 18 such that light from the image source 8 is coupled into
the first optical fibers 16. The first optical coupler 18 has a
proximal end 15 and a distal end 19.
[0080] The apparatus optionally comprises a memory unit 24 and a
user interface unit 26.
[0081] The first optical fibers 16 may be fixedly mounted to the
housing 4, i.e. the first optical fibers 16 may form a part of the
apparatus 2. Alternatively, a distal end 19 of the first optical
coupler 18 may be secured releasably to the proximal ends 17 of the
first fiber bundle 16 by a click-release-coupling.
[0082] During use, second optical fibers 20 are coupled to the
apparatus 2 at the proximal ends 21 of the second optical fibers 20
via second optical coupler 22 such that pattern sequences or images
projected on the surface region is detected by the first camera 14.
The second optical coupler 18 comprises a proximal end 23 and a
distal end 25.
[0083] The first and second optical fibers may be fixedly mounted
to the housing 4, i.e. the first and second optical fibers may form
a part of the apparatus 2, thereby simplifying setting up the
apparatus.
[0084] Alternatively, the distal end 19 of the first optical
coupler 18 and/or the distal end 25 of the second optical coupler
22 may be secured releasably to the proximal ends 17 of the first
fiber bundle 16 and the proximal ends 21 of the second fiber bundle
20, respectively, by a click-release-coupling.
[0085] The apparatus 2 is configured for projecting a first pattern
sequence (S1) onto a surface region of the subject with the image
source 10, wherein the subject is positioned in a scanner borehole
of a medical scanner, the first pattern sequence optionally
comprising a first primary pattern (P.sub.1,1) and a first
secondary pattern (P.sub.1,2). The apparatus 2 may be configured
for detecting the projected first pattern sequence (S1') with the
first camera 14. The control unit 6 optionally determines a second
pattern sequence (S2) comprising a second primary pattern
(P.sub.2,1) based on the detected first pattern sequence (S1') and
sends control signals to the image source 8 with image source 10
and light modulator 12 projecting images in the form of the second
pattern sequence (S2) onto a surface of the subject via the first
optical coupler 18. The projected second pattern sequence (S2') may
be detected with the first camera 14 and the pattern sequence data
are processed in the control unit and/or in the first camera 14
and/or in external computer 50. Upon or during detection of pattern
sequence data, the apparatus 2 or external computer 50 determines
motion tracking parameters based on the detected second pattern
sequence (S2').
[0086] FIGS. 2-5 show different embodiments of the first optical
coupler 18 comprising a plurality of lens elements I.sub.1, . . . ,
I.sub.N, including a first lens element I.sub.1 and a second lens
element I.sub.2. In FIG. 2, two lens elements are provided whereas
FIGS. 3 and 4 show a large plurality of lens elements. In FIG. 5,
the first optical coupler 18 is a relay lens coupler comprising or
consisting of a number of N lens elements positioned inside an
outer housing of the relay lens coupler. N may be six, eight or
ten.
[0087] FIGS. 2-5 show only the first optical coupler 18, however
the second optical coupler 22 may have an identical or different
construction as the embodiments shown in FIGS. 2-5 for the first
optical coupler 18. The following description of the lens elements
in the first optical coupler 18 may therefore also apply to the
lens elements in the second optical coupler 22.
[0088] Each lens element of the plurality of lens elements I.sub.1,
. . . , I.sub.N comprises a primary surface 28 facing a distal end
19 of the first optical coupler 18, and a secondary surface 29
facing a proximal end 15 of the first optical coupler 18. Normally,
there will be an even number of lens elements in the first and/or
second optical coupler 18, 22. There may be two, four, six, eight,
ten, twelve or more lens elements I.sub.1, . . . , I.sub.N.
[0089] One or more of the lens elements I.sub.N may be achromatic,
e.g. at least one of the plurality of lens elements is achromatic.
In FIG. 2-5 only chromatic lens elements are shown.
[0090] In one or more embodiments, the first lens element I.sub.1
is positioned at the proximal end 15 of the first optical coupler
18 and the second lens I.sub.2 element is positioned at the distal
end 19 of the first optical coupler 18, as shown in FIG. 2. In FIG.
2, both lens elements are chromatic. However, the first lens
element I.sub.1 and the second element I.sub.2 could also be
achromatic with convex sides pointing towards each other.
[0091] In the apparatus, mirrors and/or prisms may be used to guide
the image from the image source 8 to the first optical coupler 18.
In FIGS. 2 and 3, a mirror 7 is used for guiding the image from the
image source to the light modulator 12 from where it is guided to
the proximal end 15 of the first optical coupler 18. In FIGS. 4 and
5, the image passes from the image source 8 through a prism 9 to
the light modulator 12 from where it again passes through the prism
9 in such a manner that the image is guided directly into the
proximal end 15 of the first optical coupler 18.
[0092] The first and/or second optical coupler 18, 22 may be
adapted for either increasing or decreasing the size of the image
and/or the projected image, respectively such that the size of the
image/projected image is either larger or smaller after having
passed through the first and/or second optical coupler.
[0093] A simple schematic illustration of how the image size can be
increased or decreased using an optical coupler is shown in FIG.
6a-b. In FIG. 6a, the image size is decreased from a size d.sub.in,
of the incoming image to a size of d.sub.out of the outcoming
image, where d.sub.in>d.sub.out, whereas in FIG. 6b, the image
size is increased from d.sub.in, of the incoming image to a size of
d.sub.out, where d.sub.in>d.sub.out. The different focal length
f.sub.1, f.sub.2 of the lens elements are illustrated in the
figures.
[0094] By utilizing more than two lens elements, an improved
correction and reduced (geometric) distortion may be obtained.
Further, aberration effects are reduced. This allows the user to
control the how large a part of the image which is coupled into the
first optical fibers 16 and control the size of the projected
image, which comes out of the second optical coupler 22 after
having been collected by the second optical fibers 20.
[0095] FIGS. 7a-b show two different examples of a relay lens
couplers which may be used in the invention as the first optical
coupler 18 and/or the second optical coupler 22.
[0096] In FIG. 7a, the relay coupler comprises or consist of six
lens elements I.sub.1, I.sub.2, I.sub.3, I.sub.4, I.sub.5, 1.sub.6
arranged symmetrically such that the outermost lens elements
I.sub.1, I.sub.6 are nearly identical in size oriented such that
they are a mirror image each other. Likewise, the lens elements
I.sub.2, I.sub.5 positioned adjacent to the outermost lens elements
I.sub.1, I.sub.6 form a mirror image pair and so forth for the next
lens elements approaching the middle of the relay lens coupler.
Four of the lens elements I.sub.1, I.sub.3, I.sub.4, I.sub.6 are
planoconvex, i.e. they have a convex side and a plane side, whereas
the other two lens elements I.sub.2, I.sub.5 are biconcave, i.e.
both the primary and the secondary side of the lens elements are
concave.
[0097] FIG. 7b shows a relay lens coupler comprising ten lens
elements I.sub.1, I.sub.2, I.sub.3, I.sub.4, I.sub.5, I.sub.6,
I.sub.7, I.sub.8, I.sub.9, I.sub.10 again arranged symmetrically
with the lens elements pair wise from the two outermost lens
elements towards the centre of the relay lens coupler being mirror
images of one another. In FIG. 7a, four of the lens elements
I.sub.1, I.sub.4, I.sub.7, I.sub.10 are planoconvex, two of the
lens elements I.sub.3, I.sub.8 are biconcave, two of the lens
elements I.sub.2, I.sub.9 are biconvex, i.e. both the primary and
the secondary side of the lens elements are convex, and the last
two elements I.sub.5, I.sub.6 are planoconcave, i.e. they have a
concave side and a plane side.
[0098] The number of lens elements pairs is not limited to the
examples shown in FIG. 7a-b. Further the combination of sizes and
shapes of the lens elements may also vary, e.g. different
combinations of planoconcave, planoconvex, biconcave, and/or
biconvex lens element pairs positioned such they form a mirror
image of one another could also be imagined.
[0099] It should be noted that in addition to the exemplary
embodiments of the invention shown in the accompanying drawings,
the invention may be embodied in different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the concept of the
invention to those skilled in the art.
REFERENCES
[0100] 2 Apparatus [0101] 4 Housing [0102] 6 Control unit [0103] 7
Mirror [0104] 8 Image source [0105] 9 Prism [0106] 10 Light source
[0107] 12 Light modulator [0108] 14 First camera [0109] 15 Proximal
end of the first optical coupler [0110] 16 First optical fibers
[0111] 17 Proximal ends of first optical fibers [0112] 18 First
optical coupler [0113] 19 Distal end of the first optical coupler
[0114] 20 Second optical fibers [0115] 21 Proximal ends of second
optical fibers [0116] 22 Second optical coupler [0117] 23 Proximal
end of the second optical coupler [0118] 24 Memory [0119] 25 Distal
end of the second optical coupler [0120] 26 User interface [0121]
28 Primary surface of the lens elements [0122] 29 Secondary surface
of the lens elements [0123] 30 Medical scanner [0124] 32 Magnet
[0125] 34 Scanner housing [0126] 36 Scanner borehole [0127] 38 Head
coil [0128] 39 Scanner bed [0129] 40 Subject [0130] 42 First lens
assembly [0131] 44 Second lens assembly [0132] 46 Frame [0133] 50
Power management part [0134] 52 Wall surrounding the scanner room
[0135] 54 Optical extender [0136] I.sub.N N'th lens element [0137]
I.sub.1 First lens element [0138] I.sub.2 Second lens element
[0139] I.sub.3 Third lens element [0140] I.sub.4 Fourth lens
element [0141] I.sub.5 Fifth lens element [0142] I.sub.6 Sixth lens
element [0143] I.sub.7 Seventh lens element [0144] I.sub.8 Eights
lens element [0145] I.sub.9 Ninths lens element [0146] I.sub.10
Tenths lens element [0147] d.sub.in Size of the image before
entering the first/second optical coupler [0148] d.sub.out Size of
the image after exiting the first/second optical coupler [0149]
f.sub.1 Focal length of the first lens element [0150] f.sub.2 Focal
length of the second lens element
* * * * *